- ID:
- ivo://CDS.VizieR/J/AJ/162/52
- Title:
- Census of variable stars toward Serpens Main
- Short Name:
- J/AJ/162/52
- Date:
- 14 Mar 2022 06:55:43
- Publisher:
- CDS
- Description:
- We monitored a 3deg^2^ area toward Serpens Main in the Pan-STARRS1 r, i, and z bands from 2016 April to September. Light curves of more than 11000 stars in each band were obtained, and 143 variables have been identified. Among those, 119 variables are new discoveries, while 24 variables were previously known. We present variability classes and periods of 99 stars. Of these, 81 are located in the upper giant branch, displaying long periods, while the remaining 18 variables are pre-main-sequence objects with short periods. We also identify eight eclipsing binary systems, including the known binary V0623Ser, and derive their physical parameters. According to a clustering analysis of Gaia DR2 stars in the observed field, there are 10 variable members in Serpens Main, where six members have been classified as young stellar objects in previous studies. Here we provide color-magnitude and color-color diagrams for these variables. The color variability of most variables in the color-magnitude diagrams produces the expected displacements, while the movements of cluster members point in different directions; this behavior may be associated with accretion spots or circumstellar disks.
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522. Cep A X-Ray sources
- ID:
- ivo://CDS.VizieR/J/ApJ/626/272
- Title:
- Cep A X-Ray sources
- Short Name:
- J/ApJ/626/272
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of X-rays from both components of Cepheus A, East and West, with the XMM-Newton observatory. HH 168 joins the ranks of other energetic Herbig-Haro objects that are sources of T>=10^6^K X-ray emission. We detect 102 X-ray sources, many presumed to be premain-sequence stars on the basis of the reddening of their optical and IR counterparts.
- ID:
- ivo://CDS.VizieR/J/AJ/144/113
- Title:
- Cepheids and companions in M33 from HST images
- Short Name:
- J/AJ/144/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A precise and accurate determination of the Hubble constant based on Cepheid variables requires proper characterization of many sources of systematic error. One of these is stellar blending, which biases the measured fluxes of Cepheids and the resulting distance estimates. We study the blending of 149 Cepheid variables in M33 by matching archival Hubble Space Telescope data with images obtained at the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5m telescope, which differ by a factor of 10 in angular resolution. We find that 55%+/-4% of the Cepheids have no detectable nearby companions that could bias the WIYN V-band photometry, while the fraction of Cepheids affected below the 10% level is 73%+/-4%. The corresponding values for the I band are 60%+/-4% and 72%+/-4%, respectively. We find no statistically significant difference in blending statistics as a function of period or surface brightness. Additionally, we report all the detected companions within 2" of the Cepheids (equivalent to 9pc at the distance of M33) which may be used to derive empirical blending corrections for Cepheids at larger distances.
- ID:
- ivo://CDS.VizieR/J/A+A/428/587
- Title:
- Cepheids BVRIJHK dereddened magnitudes
- Short Name:
- J/A+A/428/587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent VINCI/VLTI observations presented in Paper I (Kervalla et al., 2004A&A...416..941K) have nearly doubled the total number of available angular diameter measurements of Cepheids. Taking advantage of the significantly larger color range covered by these observations, we derive in the present paper high precision calibrations of the surface brightness-color relations using exclusively Cepheid observations. These empirical laws allow to determine the distance to Cepheids through a Baade-Wesselink type technique. The least dispersed relations are based on visible-infrared colors, for instance FV(V-K)=-0.1336+/-0.0008(V-K)+3.9530+/-0.0006. The convergence of the Cepheid (this work) and dwarf stars (Kervella et al. 2004) visible-infrared surface brightness-color relations is strikingly good. The astrophysical dispersion of these relations appears to be very small, and below the present detection sensitivity.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/58
- Title:
- Cepheids from VVV in the southern Galactic midplane
- Short Name:
- J/ApJ/883/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The far side of the Milky Way's disk is one of the most concealed parts of the known universe due to extremely high interstellar extinction and point-source density toward low Galactic latitudes. Large time-domain photometric surveys operating in the near-infrared hold great potential for the exploration of these vast uncharted areas of our Galaxy. We conducted a census of distant classical and type II Cepheids along the southern Galactic midplane using near-infrared photometry from the VISTA Variables in the Via Lactea survey. We performed a machine-learned classification of the Cepheids based on their infrared light curves using a convolutional neural network. We have discovered 640 distant classical Cepheids with up to ~40mag of visual extinction and over 500 type II Cepheids, most of them located in the inner bulge. Intrinsic color indices of individual Cepheids were predicted from sparse photometric data using a neural network, allowing their use as accurate reddening tracers. They revealed a steep, spatially varying near-infrared extinction curve toward the inner bulge. Type II Cepheids in the Galactic bulge were also employed to measure robust mean selective-to-absolute extinction ratios. They trace a centrally concentrated spatial distribution of the old bulge population with a slight elongation, consistent with earlier results from RR Lyrae stars. Likewise, the classical Cepheids were utilized to trace the Galactic warp and various substructures of the Galactic disk and uncover significant vertical and radial age gradients of the thin disk population at the far side of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/L43
- Title:
- Cepheids HST amplitudes in V- and H-band
- Short Name:
- J/ApJ/896/L43
- Date:
- 21 Mar 2022 07:02:57
- Publisher:
- CDS
- Description:
- The accuracy of the Hubble constant measured with extragalactic Cepheids depends on robust photometry and background estimation in the presence of stellar crowding. The conventional approach accounts for crowding by sampling backgrounds near Cepheids and assuming that they match those at their positions. We show a direct consequence of crowding by unresolved sources at Cepheid sites is a reduction in the fractional amplitudes of their light curves. We use a simple analytical expression to infer crowding directly from the light curve amplitudes of >200 Cepheids in three Type Ia supernovae hosts and NGC4258 as observed by Hubble Space Telescope-the first near-infrared amplitudes measured beyond the Magellanic Clouds. Where local crowding is minimal, we find near-infrared amplitudes match Milky Way Cepheids at the same periods. At greater stellar densities we find that the empirically measured amplitudes match the values predicted (with no free parameters) from crowding assessed in the conventional way from local regions, confirming their accuracy for estimating the background at the Cepheid locations. Extragalactic Cepheid amplitudes would need to be ~20% smaller than measured to indicate additional, unrecognized crowding as a primary source of the present discrepancy in H0. Rather, we find the amplitude data constrains a systematic mis-estimate of Cepheid backgrounds to be 0.029R+/-0.037mag, more than 5x smaller than the size of the present ~0.2mag tension in H0. We conclude that systematic errors in Cepheid backgrounds do not provide a plausible resolution to the Hubble tension.
- ID:
- ivo://CDS.VizieR/J/ApJS/183/109
- Title:
- Cepheids in 3 host galaxies
- Short Name:
- J/ApJS/183/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first of two papers reporting measurements from a program to determine the Hubble constant to ~5% precision from a refurbished distance ladder. We present new observations of 110 Cepheid variables in the host galaxies of two recent Type Ia supernovae (SNe Ia), NGC 1309 and NGC 3021, using the Advanced Camera for Surveys on the Hubble Space Telescope (HST).
- ID:
- ivo://CDS.VizieR/J/AJ/156/130
- Title:
- Cepheids in M31 - PAndromeda Cepheid sample
- Short Name:
- J/AJ/156/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the largest Cepheid sample in M31 based on the complete Pan-STARRS1 survey of Andromeda (PAndromeda) in the r_P1_, i_P1_, and g_P1_ bands. We find 2686 Cepheids with 1662 fundamental-mode Cepheids, 307 first-overtone Cepheids, 278 type II Cepheids, and 439 Cepheids with undetermined Cepheid type. Using the method developed by Kodric et al. (2013, , Cat. J/AJ/145/106), we identify Cepheids by using a three-dimensional parameter space of Fourier parameters of the Cepheid light curves combined with a color cut and other selection criteria. This is an unbiased approach to identify Cepheids and results in a homogeneous Cepheid sample. The period-luminosity relations obtained for our sample have smaller dispersions than in our previous work. We find a broken slope that we previously observed with HST data in Kodric et al. (2013, , Cat. J/AJ/145/106), albeit with a lower significance.
- ID:
- ivo://CDS.VizieR/J/A+A/440/487
- Title:
- Cepheids in the young LMC cluster NGC 1866
- Short Name:
- J/A+A/440/487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new near-IR light curves for six Cepheids in the young blue LMC cluster NGC 1866 as well as high precision radial velocity curves for ten Cepheids in NGC 1866 and two in NGC 2031. For the six Cepheids in NGC 1866 with new J and K light curves we determine distances and absolute magnitudes by applying the near-IR surface brightness method. We find that the formal error estimates on the derived distances are underestimated by about a factor of two. We find excellent agreement between the absolute magnitudes for the low metallicity LMC Cepheids with the Period-Luminosity (P-L) relation determined by the near-IR surface brightness (ISB) method for Galactic Cepheids suggesting that the slope of the P-L relations for low metallicity and solar metallicity samples could be very similar in contrast to other recent findings. Still there appears to be significant disagreement between the observed slopes of the OGLE based apparent P-L relations in the LMC and the slopes derived from ISB analysis of Galactic Cepheids, and by inference for Magellanic Cloud Cepheids, indicating a possible intrinsic problem with the ISB method itself. Resolving this problem could reaffirm the P-L relation as the prime distance indicator applicable as well to metallicities significantly different from the LMC value.
- ID:
- ivo://CDS.VizieR/J/A+A/383/398
- Title:
- Cepheids multiphotometry
- Short Name:
- J/A+A/383/398
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New estimates of the distances of 36 nearby galaxies are presented based on accurate distances of galactic Cepheids obtained by Gieren et al. (1998ApJ...496...17G) from the geometrical Barnes-Evans method. The concept of ``sosie'' is applied to extend the distance determination to extragalactic Cepheids without assuming the linearity of the PL relation. Doing so, the distance moduli are obtained in a straightforward way. The correction for extinction is made using two photometric bands (V and I) according to the principles introduced by Freedman & Madore (1990ApJ...365..186F).
