- Ancillary Targets
- Transient Universe in Stripe 82
- Host Galaxies of SDSS-II SNe
- BCGs in
Stripe 82 - High-Quality LRG spectra
- Reddened
Quasars - No Quasar Left Behind
- Variability-Selected Quasars
- K-band Selected Quasars
- Low-Mass Stars and Brown Dwarfs
- Low-Mass Binary Stars
- White Dwarfs and Hot Subdwarfs
- Distant Halo
Giants - Bright
Galaxies - High-Energy Blazars in Optical
- An X-Ray View Star Formation
- Remarkable X-Ray Sources
- Star-Forming Radio Galaxies
- Galaxies Near QSO Sight Lines
- Luminous Blue Galaxies
- BAL Quasar Variability
- Variable QSO Absorption
- Double-Lobed Radio QSOs
- High-Redshift Quasars
- High-z QSOs in SDSS/UKIDSS
- BOSS Targeting
- Algorithms
The Transient Universe in Stripe 82
Summary
Spectra of a variety of variable objects in a 220-square-degree section of the repeated imaging of SDSS stripe 82
Finding Targets
An object whose ANCILLARY_TARGET1
value includes one or more of the bitmasks
in the following table was targeted for spectroscopy as part of this ancillary target program.
See SDSS-III bitmasks to learn how to use these
values to identify objects in this ancillary target program.
Sub-program (bit name) |
Bit | Target Description | Target density (deg–2) |
---|---|---|---|
AMC | 0 | Candidate Am CVn variables | 0.05 |
FLARE1 | 1 | Flaring M stars (year 1 targets) | 0.2 |
FLARE2 | 2 | Flaring M stars (year 2 targets) | 0.7 |
HPM | 3 | High Proper Motion stars | 0.5 |
LOW_MET | 4 | Low-metallicity M dwarfs | 0.3 |
VARS | 5 | Variables outside the stellar and quasar loci | 0.9 |
MTEMP | 63 | Template M-stars observed as a comparison sample | 0.5 |
Description
The repeat imaging in SDSS's Stripe 82 allows identification of transient and variable phenomena of all sorts (for example Anderson et al. 2008; Blake et al. 2008; Becker et al. 2008; Kowalski et al. 2009; Bhatti et al. 2010; Becker et al. 2011; Sako et al. 2011). In this program, several classes of variable point sources and high-proper-motion stars discovered in Stripe 82 photometry were targeted for follow-up spectroscopy with the BOSS spectrograph. Targeted objects include flaring M stars (Kowalski et al. 2009), faint high proper motion stars (Scholz et al. 2009; Schmidt et al. 2010c), candidate low-metallicity M dwarfs, and diverse samples of variable stars (Roelofs et al. 2007; Anderson et al. 2008; Blake et al. 2008).
The target selection criteria for each class of transient objects is described in the "Target selection details" section below.
Primary contact
Cullen Blake |
---|
University of Pennsylvania |
chblake -at- sas.upenn.edu |
Other contacts
Scott Anderson, Joshua S. Bloom, John Bochanski, John M. Brewer, Daryl Haggard, Suzanne Hawley, Eric Hilton, Adam Kowalski, Peter Nugent, Sarah Schmidt, Lucianne Walkowicz, and Andrew West
Target Selection Details
The target selection for this program is complicated. Each of the six sub-programs used a different target selection algorithm. The paragraphs below describe the algorithm for each sub-program.
Candidate Am CVn Stars
Consists of ten candidate Am CVn stars selected based on their variability and colors
((upsf – gpsf) > 0.4 and (gpsf – rpsf) > 0)
To identify candidate AM CVn stars in the Stripe 82 footprint, this ancillary target program used variability indices developed by Stetson (1996), which take advantage of simultaneous multi-band observations of stars with AM CVn-like colors. The color selection criteria were defined based on the colors of known AM CVn stars, but do allowed for objects bluer than any known AM CVn system.
The addition of variability information to the color-selected sample has allows a subset of variable star candidates to be defined; this subset should be more likely to contain genuine AM CVn stars. Quasars and Active Galactic Nuclei (AGN) are the dominant confusing variable sources in this region of color-space.
Flare Stars
Consists of about 200 flaring M stars selected from the Bramich et al. (2008) and Ivezić et al. (2007) catalogs with gpsf < 21.4, iPSF < 19, 0.3 < (ipsf - zpsf) < 1.3, and exhibiting a flare event in the Stripe 82 imaging data with amplitude Δu > 1 mag (Kowalski et al. 2009).
The FLARE1
and FLARE2
targets were selected using
slightly different methodologies for estimating the quiescent u-band
magnitudes of the M stars.
High Proper Motion Stars
Consists of about 100 high-proper-motion stars selected from the catalogs of Bramich et al. (2008) and Ivezić et al. (2007) with an emphasis on faint objects with high proper motions (μ > 0.1 mas/yr).
The goal of this target selection sub-program was to identify nearby low-mass stars and white dwarfs. Candidate nearby low-mass stars include faint stars (19 < zPSF < 20) with (iPSF - zPSF) > 1.5, including objects with photometric detections in z band only. Candidate nearby white dwarfs include stars with (gPSF - rPSF) ~ 0 and gPSF > 19.
Low-Metallicity M Dwarfs
Approximately 70 candidate low-metallicity M stars (flag LOW MET) were also targeted based on their colors being slightly outside the low-mass star stellar locus defined in West et al. (2005).
Other Variable Objects
Consists of ~ 200 variables with gpsf < 21.5, (gpsf – rpsf) > -0.5, and RMS variability in g band > 0.1 mag. These objects were selected to lie outside the stellar and quasar loci in (gpsf – rpsf) – (rpsf - ipsf) color-color space as defined in Fan et al. (1999).
MTEMP Stars
As part of this ancillary program, a number of spectral templates were observed as well. These include a random sample of approximately 100 M stars, designated MTEMP, selected to span the spectra range M0 to M8 following the color criteria outlined in West et al. (2005) (17.5 < iPSF < 18.5, (rpsf – ipsf) > 0.5, (ipsf – zpsf) > 0.3).
REFERENCES
Anderson, S. F., et al. 2008, AJ, 135, 2108
Becker, A. C., et al. 2008, MNRAS, 386, 416
Bhatti, W. A., Richmond, M. W., Ford, H. C., & Petro, L. D. 2010, ApJS, 186, 233
Blake, C. H., Torres, G., Bloom, J. S., & Gaudi, B. S. 2008, ApJ, 684, 635
Bramich, D. M., et al. 2008, MNRAS, 386, 887
Fan, X., et al. 1999, AJ, 118, 1
Ivezić, Ž., et al. 2004, Astronomische Nachrichten, 325, 583
Kowalski, A. F., Hawley, S. L., Hilton, E. J., Becker, A. C., West, A. A., Bochanski, J. J., & Sesar, B. 2009,
AJ, 138, 633
Roelofs, G. H. A., Nelemans, G., & Groot, P. J. 2007, MNRAS, 382, 685
Sako, M., et al. 2011, ApJ, 738, 162
Schmidt, S. J., West, A. A., Hawley, S. L., & Pineda, J. S. 2010c, AJ, 139, 1808
Scholz, R.-D., Storm, J., Knapp, G. R., & Zinnecker, H. 2009, A&A, 494, 949
Stetson, P.B., 1996, PASP, 108, 851
West, A. A., Walkowicz, L. M., & Hawley, S. L. 2005, PASP, 117, 706