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1691. YSOVAR: infrared photometry in Lynds 1688
ID:
ivo://CDS.VizieR/J/AJ/148/122
Title:
YSOVAR: infrared photometry in Lynds 1688
Short Name:
J/AJ/148/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
The emission from young stellar objects (YSOs) in the mid-infrared (mid-IR) is dominated by the inner rim of their circumstellar disks. We present IR data from the Young Stellar Object VARiability (YSOVAR) survey of ~800 objects in the direction of the Lynds 1688 (L1688) star-forming region over four visibility windows spanning 1.6yr using the Spitzer Space Telescope in its warm mission phase. Among all light curves, 57 sources are cluster members identified based on their spectral energy distribution and X-ray emission. Almost all cluster members show significant variability. The amplitude of the variability is larger in more embedded YSOs. Ten out of 57 cluster members have periodic variations in the light curves with periods typically between three and seven days, but even for those sources, significant variability in addition to the periodic signal can be seen. No period is stable over 1.6yr. Nonperiodic light curves often still show a preferred timescale of variability that is longer for more embedded sources. About half of all sources exhibit redder colors in a fainter state. This is compatible with time-variable absorption toward the YSO. The other half becomes bluer when fainter. These colors can only be explained with significant changes in the structure of the inner disk. No relation between mid-IR variability and stellar effective temperature or X-ray spectrum is found.
1692. YSOVAR: infrared photometry in NGC 1333
ID:
ivo://CDS.VizieR/J/AJ/150/175
Title:
YSOVAR: infrared photometry in NGC 1333
Short Name:
J/AJ/150/175
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of the Young Stellar Object VARiability (YSOVAR) program, we monitored NGC 1333 for ~35 days at 3.6 and 4.5{mu}m using the Spitzer Space Telescope. We report here on the mid-infrared variability of the point sources in the ~10'x~20' area centered on 03:29:06, +31:19:30 (J2000). Out of 701 light curves in either channel, we find 78 variables over the YSOVAR campaign. About half of the members are variable. The variable fraction for the most embedded spectral energy distributions (SEDs) (Class I, flat) is higher than that for less embedded SEDs (Class II), which is in turn higher than the star-like SEDs (Class III). A few objects have amplitudes (10-90th percentile brightness) in [3.6] or [4.5]>0.2mag; a more typical amplitude is 0.1-0.15mag. The largest color change is >0.2mag. There are 24 periodic objects, with 40% of them being flat SED class. This may mean that the periodic signal is primarily from the disk, not the photosphere, in those cases. We find 9 variables likely to be "dippers", where texture in the disk occults the central star, and 11 likely to be "bursters", where accretion instabilities create brightness bursts. There are 39 objects that have significant trends in [3.6]-[4.5] color over the campaign, about evenly divided between redder-when-fainter (consistent with extinction variations) and bluer-when-fainter. About a third of the 17 Class 0 and/or jet-driving sources from the literature are variable over the YSOVAR campaign, and a larger fraction (~half) are variable between the YSOVAR campaign and the cryogenic-era Spitzer observations (6-7 years), perhaps because it takes time for the envelope to respond to changes in the central source. The NGC 1333 brown dwarfs do not stand out from the stellar light curves in any way except there is a much larger fraction of periodic objects (~60% of variable brown dwarfs are periodic, compared to ~30% of the variables overall).
1693. Z CMa NW emission lines
ID:
ivo://CDS.VizieR/J/A+A/643/A29
Title:
Z CMa NW emission lines
Short Name:
J/A+A/643/A29
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use optical spectroscopy to investigate the disk, wind, and accretion during the 2008 Z CMa NW outburst. The emission lines are used to constrain the locations, densities, and temperatures of the structures around the star. Over 1000 optical emission lines reveal accretion, a variable, multi-component wind, and double-peaked lines of disk origin. The variable, non-axisymmetric, accretion-powered wind has slow (~0km/s ), intermediate (~-100km/s) and fast (>=-400km/s) components. The fast components are of stellar origin and disappear in quiescence, while the slow component is less variable and could be related to a disk wind. The changes in the optical depth of the lines between outburst and quiescence are consistent with increased accretion being responsible for the observed outburst. We derive an accretion rate of 10^-4^M_{sun}_/yr in outburst. The FeI and weak FeII lines arise from an irradiated, flared disk at ~0.5-3(M*/16M_{sun}_) au with asymmetric upper layers, revealing that the energy from the accretion burst is deposited at scales below 0.5au. Some line profiles have redshifted asymmetries, but the system is unlikely sustained by magnetospheric accretion, especially in outburst. The accretion-related structures extend over several stellar radii and, like the wind, are likely non-axisymmetric. The stellar mass may be ~6-8M_{sun}_, lower than previously thought (~16M_{sun}_). Emission line analysis is found to be a powerful tool to study the innermost regions and accretion in stars within a very large range of effective temperatures. The density ranges in the disk and accretion structures are higher than in late-type stars, but the overall behavior, including the innermost disk emission and variable wind, is very similar independently of the spectral type. Our work suggests a common outburst behavior for stars with spectral types ranging from M-type to intermediate-mass stars.
1694. ZTF light curve of 51 stars in 12 globular clusters
ID:
ivo://CDS.VizieR/J/AJ/162/63
Title:
ZTF light curve of 51 stars in 12 globular clusters
Short Name:
J/AJ/162/63
Date:
21 Mar 2022 11:55:52
Publisher:
CDS
Description:
In this work, we aimed to derive the gri-band period-luminosity (PL) and period-luminosity-color (PLC) relations for late-type contact binaries, for the first time, located in globular clusters, using the homogeneous light curves collected by the Zwicky Transient Factory (ZTF). We started with 79 contact binaries in 15 globular clusters, and retained 30 contact binaries in 10 globular clusters that have adequate numbers of data points in the ZTF light curves and are unaffected by blending. Magnitudes at mean and maximum light of these contact binaries were determined using a fourth-order Fourier expansion, while extinction corrections were done using the Bayerstar2019 3D reddening map together with adopting the homogeneous distances to their host globular clusters. After removing early-type and "anomaly" contact binaries, our derived gri-band PL and period-Wesenheit (PW) relations exhibited a much larger dispersion with large errors on the fitted coefficients. Nevertheless, the gr-band PL and PW relations based on this small sample of contact binaries in globular clusters were consistent with those based on a larger sample of nearby contact binaries. Good agreements of the PL and PW relations suggested both samples of contact binaries in the local Solar neighborhood and in the distant globular clusters can be combined and used to derive and calibrate the PL, PW, and PLC relations. The final derived gr-band PL, PW, and PLC relations were much improved over those based on the limited sample of contact binaries in the globular clusters.
1695. ZZ Ceti white dwarfs and candidates in Gaia survey
ID:
ivo://CDS.VizieR/J/AJ/160/252
Title:
ZZ Ceti white dwarfs and candidates in Gaia survey
Short Name:
J/AJ/160/252
Date:
09 Mar 2022 22:00:00
Publisher:
CDS
Description:
The Gaia satellite recently released parallax measurements for ~260000 high-confidence white dwarf candidates, allowing for precise measurements of their physical parameters. By combining these parallaxes with Pan-STARRS and u-band photometry, we measured the effective temperature and stellar mass for all white dwarfs in the Northern Hemisphere within 100pc of the Sun, and identified a sample of ZZ-Ceti white dwarf candidates within the so-called instability strip. We acquired high-speed photometric observations for 90 candidates using the PESTO camera attached to the 1.6m telescope at the Mont-Megantic Observatory. We report the discovery of 38 new ZZ-Ceti stars, including two very rare ultramassive pulsators. We also identified five possibly variable stars within the strip, in addition to 47 objects that do not appear to show any photometric variability. However, several of those could be variable with an amplitude below our detection threshold, or could be located outside the instability strip due to errors in their photometric parameters. In the light of our results, we explore the trends of the dominant period and amplitude in the M--Teff plane, and briefly discuss the question of the purity of the ZZ-Ceti instability strip (i.e., a region devoid of non-variable stars).